Golf Ball

ABSTRACT

A golf ball includes a core, an ionomer layer enclosing the core, a polyisocyanate interlayer enclosing the ionomer layer, and a thermoplastic polyurethane cover layer enclosing the polyisocyanate interlayer. The ionomer layer is physically bonded to the polyisocyanate interlayer to form a physical bonding interface therebetween, and the polyisocyanate interlayer is chemically bonded to the thermoplastic polyurethane cover layer to form a chemical bonding interface therebetween.

FIELD

The disclosure relates to a golf ball, more particularly to a multilayer golf ball having a polyisocyanate interlayer.

BACKGROUND

Most conventional golf balls are constructed of at least two layers of materials and are thus called multilayer golf balls. These multilayer golf balls come in two principal varieties: wound golf balls and solid golf balls. Solid golf balls having a single solid core and a single cover layer are the most popular commercial product among multilayer golf balls, and are generally referred to as “two-piece” golf balls.

In the multilayer golf balls, the outer layer (sometimes referred to as a mantle layer) may be formed by molding techniques such as injection molding or compression molding to mold an outer layer material around an underlying substrate or core. To meet optimal performance requirements, the outer layer is preferably bonded to the underlying substrate/core as strongly as possible.

Improper adhesion between the outer layer and the underlying substrate/core may significantly detract from the durability and performance characteristics of a golf ball, and may also adversely impact the spin characteristics of the golf ball. For example, poor adhesion may cause formation of cavities between the layers, resulting in delamination of the layers when the golf ball is subjected to impacts, and may cause loss in shear stress generated in the ball.

Golf ball manufacturers have attempted to improve adhesion between layers by forming surface features on the underlying substrate. Techniques for forming surface features on a surface of the underlying substrate include plasma treatment, high-voltage electrostatic discharge (such as corona discharge treatment), chemical polishing (such as chemical etching), or shot blast finishing. These techniques, however, are time-consuming and require additional manufacturing equipments, which may increase the costs and time of production.

Therefore, there remains a need in the art to provide a multilayer golf ball having strong bonding between layers thereof.

SUMMARY

Therefore, an object of the disclosure is to provide a golf ball that can overcome at least one of the aforesaid drawbacks associated with the prior art.

According to the disclosure, there is provided a golf ball including a core, an ionomer layer enclosing the core, a polyisocyanate interlayer enclosing the ionomer layer, and a thermoplastic polyurethane cover layer enclosing the polyisocyanate interlayer. The ionomer layer is physically bonded to the polyisocyanate interlayer to form a physical bonding interface therebetween. The polyisocyanate interlayer is chemically bonded to the thermoplastic polyurethane cover layer to form a chemical bonding interface therebetween.

DETAILED DESCRIPTION

In one embodiment of the disclosure, a golf ball includes a core, an ionomer layer enclosing the core, a polyisocyanate interlayer enclosing the ionomer layer, and a thermoplastic polyurethane cover layer enclosing the polyisocyanate interlayer. The ionomer layer is physically bonded to the polyisocyanate interlayer to form a physical bonding interface therebetween. The polyisocyanate interlayer is chemically bonded to the thermoplastic polyurethane cover layer to form a chemical bonding interface therebetween.

With the physical bonding interface and the chemical bonding interface formed in the golf ball, the core, the ionomer layer, the polyisocyanate interlayer and the thermoplastic polyurethane cover layer can be tightly bonded together.

Preferably, the core is made from a rubber material.

The ionomer layer is made from an ionomer. Preferably, the ionomer is a copolymer of olefin and α,β-ethylenically unsaturated carboxylic acid, and the ionomer has acid groups that are neutralized with metal ions.

More preferably, the ionomer is a copolymer of ethylene and methacrylic acid, and the ionomer has acid groups that are neutralized with metal ions.

Commercially available examples of the ionomer are under the trade name of Surlyn from Du Pont, such as the magnesium ion neutralized type ionomer (Surlyn 6230, Surlyn 6910, or the like), the lithium ion neutralized type ionomer (Surlyn 7930, Surlyn 7940, or the like), the sodium ion neutralized type ionomer (Surlyn 8140, Surlyn 8150, Surlyn 8320, Surlyn 8528, Surlyn 8660, Surlyn 8920, Surlyn 8940, Surlyn 8945, or the like), and the zinc ion neutralized type ionomer (Surlyn 9020, Surlyn 9120, Surlyn 9150, Surlyn 9320, Surlyn 9520, Surlyn 9650, Surlyn 9720, Surlyn 9721, Surlyn 9910, Surlyn 9945, Surlyn 9950, or the like).

Preferably, the polyisocyanate interlayer is made from a polyisocyanate composition including a polyisocyanate compound and a solvent.

Preferably, the polyisocyanate compound is selected from the group consisting of tris(4-isocyanatophenyl) thiophosphate, triphenylmethane-4,4′,4″-triisocyanate, 2,4-toluenediisocyanate polyisocyanate (TDI polyisocyanate), an adduct of trimethylolpropane and 2,4-toluenediisocyanate (TMP/TDI adduct), a trimer of 1,6-hexamethylene diisocyanate (HDI biuret), and combinations thereof.

The solvent used in the embodiment can be any solvent generally used in the art, as long as the solvent can be uniformly mixed with the polyisocyanate compound and is conducive to coating. Preferably, the solvent is selected from the group consisting of ethyl acetate, methyl ethyl ketone, and the combination thereof.

The concentration of the polyisocyanate composition may be adjusted to a proper range, such that the polyisocyanate composition can be uniformly applied to an outer surface of the ionomer layer. Preferably, the polyisocyanate compound is in an amount ranging from 5 to 30 wt % and the solvent is in an amount ranging from 70 to 95 wt % based on the total weight of the polyisocyanate composition.

Preferably, the thermoplastic polyurethand cover layer is made from a thermoplastic polyurethane. The thermoplastic polyurethane is preferably selected from the group consisting of polyether-based polyurethane, polyester-based polyurethane, polycarbonate-based polyurethane, unsaturated group-containing polyurethane, and combinations thereof.

Commercially available examples of the thermoplastic polyurethane are under the catalog numbers of 3095A and B1095A from Great Eastern Resins Industrial Co., Ltd.

According to the disclosure, a method of manufacturing the golf ball is provided. The method includes providing a core, applying the ionomer to the core so as to form the ionomer layer enclosing the core, applying the polyisocyanate composition on the outer surface of the ionomer layer so as to form the polyisocyanate interlayer enclosing the ionomer layer, and injection molding the thermoplastic polyurethane to form the thermoplastic polyurethane cover layer enclosing the polyisocyanate interlayer.

After applying the polyisocyanate composition to the outer surface of the ionomer layer, the solvent in the polyisocyanate composition is removed so as to enhance the interlayer bonding strength between the layers of the golf ball.

Formation of the thermoplastic polyurethane cover layer on a surface of the polyisocyanate interlayer can be conducted by any known injection molding method. Preferably, the thermoplastic polyurethane is injection molded onto the polyisocyanate interlayer.

EXAMPLES

The following examples are provided to illustrate the embodiment of the disclosure, and should not be construed as limiting the scope of the disclosure.

Sources of Chemicals

1.Ionomer: an ionomer mixture of two commercially available ionomers purchased from DuPont having the catalog nos.: Surlyn 8920 and Surlyn 9120, and being mixed at a weight ratio of 7:3.

2. Polyisocyanate compounds: tris(4-isocyanatophenyl) thiophosphate, triphenylmethane-4,4′,4″-triisocyanate, 2,4-toluenediisocyanate polyisocyanate, adduct of trimethylolpropane and 2,4-toluenediisocyanate, trimer of 1,6-hexamethylene diisocyanate.

3.Thermoplastic polyurethane: two thermoplastic polyurethane products purchased from Great Eastern Resins Industrial Co., Ltd., and having the catalog nos.: 3095A and B1095A. Before use, the thermoplastic polyurethane was dehumidified under 95° C. for 6 hours.

Example 1-I (EX1-I)

The above mentioned ionomer mixture was subjected to injection molding to form an ionomer layer. The ionomer layer was cut into a test sample with a size of 2.54 cm×10 cm×0.4 cm.

15wt % of the tris(4-isocyanatophenyl) thiophosphate and 85 wt % of ethyl acetate were mixed to obtain a polyisocyanate composition. The polyisocyanate composition was coated on the test sample by a brush so as to form a polyisocyanate interlayer. The test sample coated with the polyisocyanate composition was then placed in an oven under a drying temperature for 5 minutes to remove ethyl acetate. The drying temperature was 80° C.

The test sample having the polyisocyanate interlayer was subsequently placed in a mold. The B1095A thermoplastic polyurethane was injection molded to form a thermoplastic polyurethane cover layer on the polyisocyanate interlayer, then cooled for 2 hours to forma composite structure. The injection molding was conducted under a temperature ranging from 205 to 215° C.

The composite structure of Example 1-I includes the ionomer, layer, the polyisocyanate interlayer, and the thermoplastic polyurethane cover layer.

Example 2-I to 5-I (EX2-I to EX5-I)

The composite structures of Examples 2-I to 5-I were prepared under conditions similar to those of Examples 1-I except for a difference in the type of polyisocyanate compounds (see Table 1) used.

Example 1-II (EX1-II)

The composite structure of Example 1-II was prepared under conditions similar to those of Examples 1-I except that Example 1-II used the thermoplastic polyurethane under the catalog number 3095A.

Example 2-11 to 5-II (EX2-II to EX5-II)

The composite structures of Examples 2-II to 5-II were prepared under conditions similar to those of Examples 1-II except for a difference in the type of polyisocyanate compounds (see Table 1) used.

Comparative Example I (CEI)

The above mentioned ionomer mixture was subjected to injection molding to form an ionomer layer. The ionomer layer was cut into a test sample with a size of 2.54 cm×10 cm×0.4 cm.

The B1095A thermoplastic polyurethane was injection molded to form a thermoplastic polyurethane cover layer on the ionomer layer. The injection molding was conducted under a temperature ranging from 205 to 215° C., which was followed by cooling of the thermoplastic polyurethane cover layer for 2 hours to form a composite structure.

Comparative Example II (CEII)

The composite structure of Comparative Example II was prepared under conditions similar to those of Comparative Example I except that Comparative Example II used the thermoplastic polyurethane of the catalog number 3095A.

Performance Tests Peeling Strength

Each composite structure of Examples 1-I to 5-I, Examples 1-II to 5-II and Comparative Examples I and II was subjected to the peeling strength test according to ASTM D-1876 standards.

The results are shown in Table 1.

TABLE 1 Peeling Strength (Kg/in) Thermoplastic polyurethane No. B1095A 3095A Polyisocyanate compounds Group I II Tris (4-isocyanatophenyl) thiophosphate EX 1 9.2 10.2 Triphenylmethane-4,4′,4″- 2 2.5 2.9 triisocyanate 2,4-toluenediisocyanate 3 3.7 3.4 polyisocyanate Trimethylolpropane/2,4-toluenediisocyanate 4 3.0 2.5 Trimer of 5 2.2 1.9 1,6-hexamethylene diisocyanate None CE 0.0 0.0

As shown in Table 1, the peeling strength of each of Examples 1-I to 5-I and 1-II to 5-11 is much greater than those of Comparative Examples I and II. The result indicates that the golf ball which includes the polyisocyanate interlayer has better interlayer bonding strength.

To sum up, with the inclusion of the polyisocyanate interlayer, which forms the physical bonding interface with the ionomer layer and the chemical bonding interface with the thermoplastic polyurethane cover layer, in the golf ball of the disclosure, the interlayer bonding strength in the multilayer golf ball could be improved.

While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation and equivalent arrangements. 

1. A golf ball comprising: a core; an ionomer layer enclosing said core; a polyisocyanate interlayer that is mainly composed of a polyisocyanate compound and that encloses said ionomer layer; and a thermoplastic polyurethane cover layer enclosing said polyisocyanate interlayer; wherein said ionomer layer is physically bonded to said polyisocyanate interlayer to form a physical bonding interface therebetween; and wherein said polyisocyanate interlayer is chemically bonded to said thermoplastic polyurethane cover layer to form a chemical bonding interface therebetween.
 2. The golf ball according to claim 1, wherein said polyisocyanate interlayer is made from a polyisocyanate composition including the polyisocyanate compound and a solvent.
 3. The golf ball according to claim 1, wherein said polyisocyanate compound is selected from the group consisting of tris(4-isocyanatophenyl) thiophosphate, triphenylmethane-4,4′,4″-triisocyanate, 2,4-toluenediisocyanate polyisocyanate, adduct of trimethylolpropane and 2,4-toluenediisocyanate, trimer of 1,6-hexamethylene diisocyanate, and combinations thereof.
 4. The golf ball according to claim 2, wherein said solvent is selected from the group consisting of ethyl acetate, methyl ethyl ketone, and the combination thereof.
 5. The golf ball according to claim 1, wherein said ionomer layer is made from an ionomer, said ionomer being a copolymer of an olefin and α,β-ethylenically unsaturated carboxylic acid, said ionomer having acid groups that are neutralized with metal ions.
 6. The golf ball according to claim 1, wherein said ionomer is a copolymer of ethylene and methacrylic acid copolymer, said ionomer having acid groups that are neutralized with metal ions.
 7. The golf ball according to claim 1, wherein said thermoplastic polyurethane cover layer is made from a thermoplastic polyurethane, said thermoplastic polyurethane being selected from the group consisting of polyether based polyurethane, polyester based polyurethane, polycarbonate based polyurethane, unsaturated group-containing polyurethane, and combinations thereof. 